Absorbent articles comprising an organic zinc salt and an anti-bacterial agent or alkali metal chloride or alkaline earth metal chloride

ABSTRACT

An absorbent article, such as a diaper, panty diaper, sanitary napkin or incontinence device includes a topsheet, a backsheet and an absorbent core enclosed between the topsheet and the backsheet. The absorbent core includes an anti-bacterial agent or an alkali metal or alkaline earth metal chloride in combination with an organic zinc salt, in particular, zinc ricinoleate. The combination of antibacterial or (earth) alkali metal chloride and organic zinc salt exerts a synergetic effect in the suppression of malodours, such as ammonia.

The present invention relates to an absorbent article such as a diaper,panty diaper, sanitary napkin or incontinence device comprising aneffective odour control system. The present invention relates inparticular to such absorbent articles wherein an organic zinc salt sucha zinc ricinoleate and an anti-bacterial agent or alkali metal chlorideor alkaline earth metal chloride interact to reduce malodours such asammonia.

TECHNICAL BACKGROUND

One important area of development in the area of absorbent articles ofthe above-mentioned type is the control of odourous compounds formingtypically after the release of body fluids, especially over a longerperiod of time. These compounds include fatty acids, ammonia, amines,sulphur-containing compounds and ketones and aldehydes. They are presentas natural ingredients of body fluids or result from degradationprocesses of natural ingredients such as urea, which are frequentlyassisted by microorganisms occurring in the urogenital flora.

Various approaches exist to suppress the formation of unpleasant odoursin absorbent articles. WO 97/46188, WO 97/46190, WO 97/46192, WO97/46193, WO 97/46195 and WO 97/46196 teach for instance theincorporation of odour inhibiting additives or deodorants such aszeolites and silica. The absorption of bodily liquids reduces howeverthe odour inhibiting capacity of zeolites as soon as these becomesaturated with water, as mentioned for instance in WO 98/17239.

A second approach involves the addition of lactobacilli with theintention of inhibiting malodour-forming bacteria in the product. Theincorporation of lactobacilli and their favourable effect are disclosedfor instance in SE 9703669-3, SE 9502588-8, WO 92/13577, SE 9801951-6and SE 9804390-4.

Another approach is the use of partially neutralized superabsorbentmaterials (acidic superabsorbent materials) (see WO 98/57677, WO00/35503 and WO 00/35505).

Therefore, an ongoing demand exists in the art for effectiveodour-control systems in absorbent articles. In particular, it would bedesirable to provide an odour-control system which achieves efficientodour reduction while maintaining the bacterial flora in the urogenitalregion.

US 2006/0036223 and US 2006/0036222 disclose absorbent articlescomprising a bodily exudate modifying agent, a skin care formulation,and a bodily exudate modifying agent neutralizer. The latter may be anenzyme inhibitor which can be selected from a large group of compoundsincluding zinc salts of both saturated and unsaturated monocarboxylicacids. Optionally, the skin care formulation comprises a furtheringredient selected from the group comprising amongst many other memberspreservatives, antimicrobial actives and antifungal actives. US2006/0036223 and US 2006/0036222 aim at reducing the viscosity of bodilyexudates to facilitate absorption of the exudates into the absorbentarticle. Odour reduction is not an issue.

EP-A-165 074 describes a hydrophilic polymer material, e.g. for themanufacture of sanitary napkins and diapers. The hydrophilic polymermaterial can be produced by a process during which a specific hydrogelis dried and may be contacted with an aqueous solution. Apart fromelectrolytes, nutrients, physiologically active polypeptides andproteins, the aqueous solution may also contain antibacterial agents.Moreover, zinc ions may be incorporated into the hydrogel, e.g. in theform of zinc sulphate or a salt of an acidic amino acid. Zinc ions arestated as having a beneficial effect on cell growth. Odour reduction isnot addressed in the reference.

The bacteriostatic, bactericidal and antifungal compositions of EP-A-0366 869 comprise lysozyme, a mineral component and an immunomodulatingagent. The mineral component, which is stated as enhancing themycobactericidal effect of lysozyme, may comprise zinc and/or iodine(Claim 5). Zinc can be provided as zinc sulfate, zinc oxide, zincgluconate and other salts and compounds of zinc. The immunomodulatingagent contained in the composition may be selected from, among manyothers, benzoic acid.

U.S. Pat. Nos. 5,721,295 and 5,847,031 relate to absorbent polymercompositions comprising an ionic or covalent cross-linking agent. Theionic cross-linking agent may be a metallic compound selected from thegroup consisting of water-soluble magnesium, calcium, aluminum,zirconium, iron and zinc compounds (cf. Claims 6 and 21 of D8a; andClaims 6 and 19 of D8b). The zinc compounds may be the salts ofinorganic acids or carboxylic acids. A huge many of suitable covalentcross-linking agents is mentioned in the reference, amongst those citricacid. U.S. Pat. Nos. 5,721,295 and 5,847,031 further describe an activesubstance-containing composition comprising the absorbent polymercomposition and at least one active substance, which may be selectedfrom the group consisting of drugs, pesticides, bactericides andperfumes. The focus of the references is on biodegradability, and odourreduction is not an issue.

U.S. Pat. No. 6,015,547 relates to a storage clarity-stable aqueous oraqueous/alcoholic solution of zinc ions in the presence of at least oneof bicarbonate and carbonate ions. The solution comprises a zinc salt ofa first anion. Optionally, the solution may contain antibacterialagents. The gist of the patent is on combining zinc ion containingcompounds and bicarbonate and/or carbonate ion containing compounds eachof which is in solution, i.e. without liberation of carbon dioxide andwithout the formation of insoluble basic salts of zinc and carbonate.

The articles for applying a skin care composition to the skin inaccordance with U.S. Pat. No. 6,153,209 may comprise a skin care agentwhich, amongst a large number of compounds, may be zinc acetate.Antibacterial actives are mentioned in a long list of furtheringredients. However, the reference does not suggest any effect in termsof odour reduction by using a combination of an organic zinc salt, suchas zinc acetate and a preservative.

U.S. Pat. No. 7,005,557; US 2003/0077307 and US 2006/0064068 relate toarticles, in particular disposable absorbent articles having afilm-forming composition comprising a viscosity enhancing agent, andoptionally anti-microbials (selected from a lengthy group). Thedocuments provide a very long list of viscosity enhancing agentsincluding metal ester complexes of aluminum, magnesium, or zinc withstearates, behenates, palmitates or laureates. The object of thesedocuments is not the reduction of odour but the formation of aprotective barrier against fluids, body exudates and other irritants.

The highly swellable absorption medium of US 2004/0213892 comprises atleast one Lewis acid as a coating agent. A large number of suitableLewis acids is provided, amongst those benzoic acid, citric acid andwater-soluble acetates, formates, oxalates or lactates of inter aliazinc. However, the document fails to disclose a preservative incombination with an organic zinc salt. Moreover, the object of US2004/0213892 is on a reduced caking tendency in a moist environmentand/or at high temperatures, whereas odour reduction is not an issue.

US 2005/0101927 is concerned with moisturizing and lubricatingcompositions which may be used on absorbent products. The absorbentproducts comprise an immobilizing agent. Many compounds, including zincstearate, are stated as being suitable as the immobilizing agent. Whilethe optional addition of preservatives is envisaged, odour reduction isnot an issue.

WO 99/00090 relates to a faecal management device which comprises aspecific bag comprising a moisture vapour permeable wall material.According to a specific embodiment, the wall material further comprisesan odour control agent. Many odour control agents are exemplified,amongst those zinc ricinoleate and, as a different type of odour controlagents, antimicrobics such as benzoic and sorbic acid. However, WO99/00090 fails to disclose a preservative and organic zinc salt incombination for achieving malodour reduction. In particular, thefunction of zinc ricinoleate as an ammonia absorber is not addressed.

WO 99/30753 is concerned with odour control particles for use inabsorbent articles. The odour control particles comprise an effectiveamount of a liquid activated particle separating means. There are twokinds of these separating means, namely physical and chemical ones.Sodium chloride (NaCl) is given as an example of a physical separatingmeans. Citric acid is exemplified as a chemical separating means. Theodour control particles for absorbent particles comprise odour controlactive materials, amongst those zinc cations. Any other known odourcontrol active is referred to as being likewise suitable for combatingmalodours. No organic zinc salt is mentioned in WO 99/30753.

DE 10256569 A1 relates to water-absorbing, crosslinked, acidgroup-containing polymers in the form of mainly open-cell foamcomprising at least one odour control agent selected from compounds withan anhydride group, compounds with an acidic group, cyclodextranes,bactericides and surfactants with an HLB value of less than 12. Oneexample of bactericidal compounds are zinc compounds such as zincchloride. However, no organic zinc salt is mentioned in this reference.

From other technical areas it is further known that organic zinc saltsof unsaturated hydroxylated fatty acids such as zinc ricinoleate aredeodorizing active ingredients (see for instance DE-A-1792074,DE-A-2548344 and DE-A-3808114).

As will be appreciated from the above, the prior art is not aware of thefavorable, in particular synergistic effects of using an antibacterialor alkali metal chloride in combination with an organic zinc salt.

It is one technical object of the present invention to overcomedeficiencies discussed above in connection with the prior art.

It is one further technical object to provide an absorbent articlehaving an efficient odour control system.

It is one further technical object of the present invention toconsiderably reduce or eliminate ammonia formation in absorbentarticles.

Further objects will become apparent from the following description ofthe invention.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to an absorbent article, such as a diaper,panty diaper, panty liner, sanitary napkin or incontinence devicecomprising a topsheet, a backsheet and an absorbent core enclosedbetween said topsheet and said backsheet, wherein said absorbent corecomprises

-   (i) an anti-bacterial agent or, in an amount of at least 0.01 g/g of    said absorbent core, at least one alkali metal or alkaline earth    metal chloride, and-   (ii) an organic zinc salt.

The present inventors have found that anti-bacterial agents and organiczinc salt, such as zinc ricinoleate interact favorably in thesuppression of unpleasant odours.

The same observation was made with alkali metal or alkaline earth metalchlorides such as NaCl. Although these normally are not referred to as“antibacterial” they control bacterial growth when used in higherconcentration.

Without wishing to be bound by theory, the mechanism underlying theodour reduction of the present invention is assumed to be as follows. Itwas found that the ammonia which produces the malodour in absorbentproducts, such as incontinence products is formed in the following way:Bacteria+Urea→NH₃

In the present invention, the antibacterial, e.g. the benzoic acid, oralkali metal chloride has the function of suppressing bacterial growthwhile the organic zinc salt, e.g. the zinc ricinoleate removes theammonia (NH₃) actually formed.

The aim of the present invention is to develop an absorbent articlewhere the amount of unwanted bacteria, such as ammonia-producingbacteria does not increase during use.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the specification and claims, the use of “comprising” isintended to cover also the more restricting meanings “essentiallyconsisting of” and “consisting”.

As “absorbent article” we understand articles capable of absorbing bodyfluids such as urine, watery feces, female secretion or menstrualfluids. These absorbent articles include, but are not limited todiapers, panty diapers, panty liners, sanitary napkins or incontinencedevice (as used for instance for adults).

Such absorbent articles have a liquid-pervious topsheet, which duringuse is facing the wearer's body. They further comprise a (preferablyliquid-impervious) backsheet, for instance a plastic film, aplastic-coated nonwoven or a hydrophobic nonwoven and an absorbent coreenclosed between the liquid-pervious topsheet and the backsheet.

A suitable topsheet may be manufactured from a wide range of materialssuch as woven and nonwoven materials (e.g. a nonwoven web of fibers),polymeric materials such as apertured plastic films, e.g. aperturedformed thermoplastic films and hydroformed thermoplastic films; porousfoams; reticulated foams; reticulated thermoplastic films; andthermoplastic scrims. Suitable woven and nonwoven materials can becomprised of natural fibers (e.g. wood or cotton fibers), syntheticfibers (e.g. polymeric fibers such as polyesters, polypropylene orpolyethylene fibers) or from a combination of natural and syntheticfibers. When the topsheet comprises a nonwoven web, the web may bemanufactured by a wide number of known techniques. For example, the webmay be spun-bonded, carded, wet-laid, melt-blown, hydroentangled,combinations of the above or the like. In accordance with the invention,it is preferred to make use of apertured plastic films (e.g.thermoplastic films) or nonwoven materials based on synthetic fibers,e.g. those made from polyethylene or polypropylene homo- or copolymersand polymer compositions based thereon.

Optionally, at least one further layer exists between the absorbent coreand the topsheet and may be made from hydrophobic and hydrophilic web orfoam materials. As “web material” we understand coherent flatfiber-based structures of paper tissue, woven or nonwoven type. Thenonwoven material may have the same features as described above fortopsheets.

Specifically, the at least one further layer may contribute to fluidmanagement, for instance in the form of at least oneacquisition/distribution layer. Such structures are taught for instanceby U.S. Pat. No. 5,558,655, EP 0 640 330 A1, EP 0 631 768 A1 or WO95/01147.

“Foam materials” are also well known in the art and for instancedescribe in EP 0 878 481 A1 or EP 1 217 978 A1 in the name of thepresent applicant.

The absorbent core may be partially or totally surrounded by a corewrap. It comprises an absorbent material that is generally compressible,conformable, non-irritating to the wearer's skin and capable ofabsorbing and retaining liquids such as urine and other body exudates.

Examples for absorbent materials include a wide variety ofliquid-absorbent materials commonly used in disposable diapers and otherabsorbent articles such as comminuted wood pulp, which is generallyreferred to as air felt or fluff, as well as creped cellulose wadding;melt blown polymers, including co-form; chemically stiffened, modifiedor cross-linked cellulosic fibers; tissue, including tissue wraps andtissue laminates, absorbent foams, absorbent sponges, superabsorbentpolymers (such as superabsorbent fibers or particles), absorbent gellingmaterials, or any other known absorbent materials or combinations ofmaterials.

The fibers typically present in the absorbent core are preferably alsocapable of absorbing body liquid as is the case for hydrophilic fibers.Most preferably the fibers are cellulosic fibers such as wood pulpfluff, cotton, cotton linters, rayon, cellulose acetate and the like,the use of cellulosic fluff pulp being preferred. The cellulosic fluffpulp can be of mechanical or chemical type, the chemical pulp beingpreferred.

The absorbent core preferably comprises suberabsorbent polymers and/orcellulosic fluff pulp fibers. If used in admixture, the SAP/fluff pulpweight ratio is preferably 20/80 to 70/30, e.g. 30/70 to 60/40.

The term “superabsorbent polymers” is well known in the art anddesignates water-swellable, water-insoluble materials capable ofabsorbing the multiple of their own weight in body fluids. Preferably,the superabsorbent polymer (SAP) is capable of absorbing at least about10 times its weight, preferably at least about 15 times its weight, inparticular at least about 20 times its weight in an aqueous solutioncontaining 0.9 wt.-% of sodium chloride (under usual measuringconditions where the superabsorbent surface is freely accessible to theliquid to be absorbed). To determine the absorption capacity of thesuperabsorbent polymer, the standard test EDANA WSP 241.2 can be used.

The superabsorbent polymer may be in any form suitable for use inabsorbent articles including particles, fibers, flakes, spheres and thelike, the particle form being preferred.

According to one embodiment, the superabsorbent polymer in the absorbentcore comprises an acidic superabsorbent since acidic components mayexert a beneficial influence on odour control. In an alternativeembodiment, the absorbent core in the absorbent article does not containan acidic superabsorbent material, in particular an acidicsuperabsorbent material having a pH of • 5.5. Thereby, the pH of bothstandard (i.e. non-acidic) and acidic SAP is measured using the standardtest EDANA WSP 200.2.

SAPs are based on homo- or copolymers comprising at least onepolymerizable unit having an acidic group (e.g. a carboxylic acid groupor a sulfonic acid group) such as methacrylic acid, acrylic acid, maleicacid, vinylsulfonic acid. The corresponding polymers include, but arenot limited to poly(meth)acrylic acids, ethylene maleic anhydridecopolymers, polymers and copolymers of vinylsulfonic acids,polyacrylates, acrylic acid grafted starch and isobutylene maleicanhydride copolymers. These polymers are preferably crosslinked torender the materials substantially water insoluble. According to onepreferred embodiment of the present invention, the superabsorbentmaterial is a crosslinked homo- or copolymer comprising (meth)acrylicacid units, for instance of the type disclosed in EP 0 391 108 A2.Standard SAPs have a pH which lies e.g. in a range of 5.8 or more.

An “anti-bacterial agent” is defined in the present invention as acompound which is able to either kill bacteria, such asammonia-generating bacteria which exist in the urogenital region ofhumans, or to suppress the growth of said bacteria.

Preferred anti-bacterial agents are capable of yielding when starting ata concentration of about 10³ CFU/ml. liquid for each type of bacteria(CFU is colony-forming unit) and at a given concentration of theanti-bacterial agent (e.g. 10⁻³ g/g dry absorbent core) an amount ofbacteria after 12 hours of 10⁵ CFU/ml liquid for each type of bacteriaor lower, preferably 10⁴-10 and more preferably 10³-10². This can bemeasured in line with the method “measuring bacteria inhibition inabsorbent bodies” as described in WO 00/35505 (page 17, method 3) in thename of the present applicant. The absorbent core used in the abovemethod preferably is circular, has a diameter of 5 cm, the amount ofabsorbent material present in the core is 1.16 g and the absorbent corehas been compressed to a bulk of about 8-10 cm³/g, and to this 16 ml oftest liquid is added. This method evaluates the capacity to suppress thegrowth of or to kill at least one bacterial strain selected from thespecies Escherichia coli, Proteus mirabilis and Enterococcus faecalis.

Anti-bacterial agents for use in the present invention are preferablycompounds which are skin-friendly. It needs to be borne in mind that theskin area being in contact with absorbent products such as diaper, pantydiaper, sanitary napkin or incontinence device is sensitive anddelicate. Anti-bacterial agents which are approved for the use in food(e.g. as preservatives) are therefore used with preference (for instancethose food preservatives being approved at the priority of the presentapplication in any EC member state or the US or Japan).

The anti-bacterial agent may be organic or inorganic. It may forinstance be selected from the following organic compounds:isothiazolinones and benzisothiazolinones, oxazolidines, pyridines,optionally chlorinated phenols, bromo compounds, aldehyde and dialdehydecompounds, benzyl alcohols, cresols, p-hydroxybenzoic acids and theiresters and salts (parabene compounds), organic acids and their salts, inparticular alkali metal and earth alkaline metal salts and organicpolyacids and their salts, in particular alkali metal and earth alkalinemetal salts. An anti-bacterial agent belongs to the above classes if itdisplays (comprises) the corresponding structural features. Accordingly,(further) substituted members such as hydroxylated organic acids arealso covered by the above classes.

The inorganic anti-bacterial agent may be selected from sulfites,bisulfites, nitrates, nitrites and iodates of alkali metals such assodium and potassium or earth alkaline metals such as calcium ormagnesium.

Preferably, one of the following compounds or a mixture thereof is usedas an anti-bacterial agent.

-   1,2-benzisothiazoline-3-one (BIT, Proxel);-   benzoic acid, E 210;-   benzyl alcohol;-   2-benzyl-4-chlorophenol (Chlorophene);-   1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4;-   5-bromo-5-nitro-1,3-dioxane (Bronidox™);-   2-bromo-2-nitropropane-1,3-diol (BNPD);-   succinic acid dialdehyde;-   dehydroacetic acid (6-methylacetopyranone);-   diazolidinyl urea (Germall II™);-   1,2-dibromo-2,4-dicyanobutane;-   6,6-dibromo-4,4-dichloro-2,2′-methylenediphenol;-   3,3′-dibromo-4,4′-hexamethylene dioxydibenzamindine    (dibromohexamidine);-   2,4-dichlorobenzyl alcohol;-   5,5′-dichloro-2,2′-dihydroxydiphenylmethane (Dichlorophen);-   4,4-dimethyl-1,3-oxazolidine;-   phenols, e.g. o-phenylphenol;-   cresols, e.g. o-, m- or p-cresol, 4-isopropyl-m-cresol,    p-chloro-m-cresol;-   2-phenoxyethanol (ethylene glycol monophenyl ether);-   1-phenoxypropane-2-ol;-   o-phenylphenol and salts thereof;-   phenyl mercury silver salts including borates;-   formaldehyde;-   fumaric acid, E 297;-   glutaraldehyde;-   glyoxal;-   hexetidine;-   hexamethylenetetramine, E 239;-   p-hydroxybenzoic acid (4-hydroxybenzoic acid);-   p-hydroxybenzoic acid-benzylester (benzyl parabene);-   p-hydroxybenzoic acid-n-butylester (butyl parabene);-   p-hydroxybenzoic acid-ethylester, E 214 (ethyl parabene);-   p-hydroxybenzoic acid-ethylester sodium salt, E 215 (ethylparabene    sodium salt);-   p-hydroxybenzoic acid-n-heptylester (heptyl parabene);-   p-hydroxybenzoic acid-methylester, E 218 (methyl parabene);-   p-hydroxybenzoic acid-methylester sodium salt, E 219 (methyl    parabene sodium salt);-   p-hydroxybenzoic acid-n-propylester, E 216 (propyl parabene);-   p-hydroxybenzoic acid-n-propylester sodium salt, E 217 (propyl    parabene sodium salt);-   1-hydroxy-4-methyl-6(2,4,4-trimethylpentyl)-2-pyridone;    imidazolidinyl urea;-   calcium acetate, E 263;-   calcium bisulfite, E 227;-   calcium propionate, E 282;-   calcium sulfite, E 226;-   potassium disulfite, E 224 (potassiumpyrosulfite);-   potassium nitrate, E 252;-   potassium propionate, E 283;-   potassium sorbate, E 202;-   2-chloracetamide;-   N-(3-chloroallyl)-hexaminiumchloride (Quaternium 15);-   1-(4-chlorphenoxy)-1-(imidazol-1-yl)-3,3-dimethylbutan-2-one;-   Chlorhexidine;-   p-chloro-m-xylenole;-   5-chloro-2-methyl-4-isothiazoline-3-one;-   4-chloro-3,5-xylenole;-   metenamine-3-chloroallylchloride;-   n,n′-methylenebis(5-methyl-oxazolidine) (Grotan OD™);-   2,2′-methylene-bis-(3,4,6-trichlorophenol) (Hexachlorophene);-   lactic acid E 270;-   myristic acid;-   natamycin, E 235 (Pimaricin);-   sodium acetate, E 262;-   sodium benzoate, E 211;-   sodium diacetate, E 262;-   sodium forminate, E 237;-   sodium nitrate, E 251;-   sodium nitrite, E 250;-   sodium propionate, E 281;-   sodium-2-pyridinethiol-1-oxide (Omadin™ and PyrionNa™);-   sodium sorbate, E 201;-   sodium sulfite, E 221;-   sodium disulfite, E 223 (sodium pyrosulfite);-   sodium iodate;-   sodium hydrogensulfite, E 222 (sodium bisulfite);-   Nisin, E 234;-   2-n-octyl-4-isothiazoline-3-one (Kathon 893™ and Skane M-8™);-   Paraformaldehyde;-   poly(1-hexamethylene biguanide hydrochloride);-   propionic acid, E 280;-   salicylic acid (2-hydroxybenzoic acid);-   sorbic acid, E 200;-   inorganic sulfites;-   sulfur dioxide (aq.), E 220;-   2,2′-thio-bis-(4,6-dichlorophenol) (Bithionol);-   Thiomersal (ethyl mercury thiosalicylate);-   1,3,5-triazine-1,3,5-(2H, 4H, 6H)-triethanol;-   trichlocarban (3,4,4′-trichlorocarbanilide);-   2,4,4′-trichloro-2′-hydroxydiphenylether (Irgasan DP300™ and    Triclosan™);-   3,4,4-trimethyl-1,3-oxazolidine (Bioban CS1135™ and Oxaben A™);-   undecene acid;-   inorganic hydrogensulfites;-   zinc-bis-(2-pyridinethiol-1-oxide) (Zink-Omadin™);-   malic acid, E 296 (hydroxy succinic acid);-   acetic acid, E 260;-   morpholine derivatives, e.g. 4-(nitrobutyl)-morpholine and-   4,4′-(2-ethyl-2-nitro-trimethylene)-dimorpholine (Bioban P 1487™ or    Bioban CS1248™);-   oxazolidines;-   pyridine derivatives;-   Kathon CG (mixture of 5-chloro-2-methyl-4-isothiazoline-3-one and    2-methyl-4-isothiazoline-3-one); and-   1,1,1-trichloro-2-methyl-2-propanol (chlorobutanol).

The anti-bacterial agent is preferably selected from organic acids andpolyacids (e.g. diacids or triacids), and their salts. The organic(poly)acid may be substituted by one, two or more hydroxy groups. Theorganic (poly)acid may be an unsaturated (e.g. mono- or diunsaturated)or saturated, linear or branched aliphatic carboxylic acid preferablyhaving from 2 to 18 carbon atoms, more preferably 3 to 8 carbon atoms.Examples thereof were already mentioned in the above list. The organicacid may also represent an aromatic (poly)acid, preferably aphenyl(poly)carboxy acid, having preferably from 7 to 18 carbon atoms,in particular 7 to 10 carbon atoms as in benzoic acid, p-hydroxybenzoicacid or salicylic acid. The salt is preferably an alkali metal (e.g. Kor Na) or earth alkaline metal salt (e.g. Ca or Mg).

Acidic anti-bacterial agents, including the above organic (poly)acidsare preferably weak acids, in particular those having a pK value of atleast 3, in particular at least 4, e.g. 4 to 5 (for polyacids the pK1value) measured in water at 25° C. Acetic acid has for instance a pK of4.75, sorbic acid a pK of 4.76 and benzoic acid a pK of 4.19.

More preferably benzoic acid, sorbic acid, tartaric acid or citric acid,most preferably benzoic acid, are used as the anti-bacterial agent inthe present invention.

The alkali metal chloride may be potassium chloride (KCl) or sodiumchloride (NaCl) and is preferably NaCl. The alkaline earth metalchloride may be magnesium chloride (MgCl₂) or calcium chloride (CaCl₂).According to the invention, the alkali metal chloride or alkaline earthmetal chloride is present in an amount of at least 0.01, preferably atleast 0.05, more preferably at least 0.1 g per g dry absorbent core.

There are no specific restrictions regarding the organic zinc salt to beused in combination with the component (i). In accordance with thepresent invention, zinc salts of organic carboxylic acids having 2 to 30carbon atoms, in particular 12 to 24 carbon atoms are preferably used.The carboxylic acid group may be attached to aliphatic,aliphatic-aromatic, aromatic-aliphatic, alicyclic, or aromatic residues,wherein the aliphatic chain or the alicyclic ring(s) may be unsaturatedand are optionally substituted, for instance by hydroxy or C1 to C4alkyl. These salts include zinc acetate, zinc lactate, zinc ricinoleateand zinc abietate. More preferably, the zinc salt is the zinc salt of anunsaturated hydroxylated fatty acid having 8 to 18 carbon atoms.Although there is no specific restriction regarding the number ofunsaturated double bonds or hydroxy groups, those fatty acids having oneor two unsaturated double bonds and one or two hydroxyl groups seem tobe preferred. The most preferred embodiment is zinc ricinoleate. Theorganic zinc salt may also be activated by the presence of amino acidsas in TEGO® Sorb available from Degussa. Further, the organic zinc saltto be used in the present invention may also be capable of removingmalodorous substances chemically based on amines, e.g., nicotine incigarette smoke, thiocompounds, e.g., allicin in garlic and onions, andacids, e.g., isovaleric acid in human sweat, and butyric acid. Forinstance, zinc ricinoleate which is, e.g., marketed by Degussa under thetradename TEGO® Sorb has the described additional odor removing effectapart from removing ammonia.

According to a particular preferred embodiment, the anti-bacterial agent(as one alternative of component (i)) is selected from the groupconsisting of benzoic acid, sorbic acid, tartaric acid and citric acid,or a mixture thereof, and the organic zinc salt is zinc ricinoleate.According to still further preferred embodiments, sodium chloride isused as component (i), and the organic zinc salt is zinc ricinoleate.

As regards the amount of component (i) and organic zinc salt to be usedin the present invention, there are no specific restrictions. In thepresent specification, these amounts are expressed in relation to theweight (in g) of the dry absorbent core. Herein the term “dry” used inrelation to the absorbent core is to be understood such that no waterhas been added to the absorbent core and that the only water present inthe absorbent core is the unavoidable residual water from manufacturing.For the purpose of the present invention, an absorbent core ispreferably regarded as “dry” after a circular test core having athickness of 5 to 6 mm, a diameter of 5 cm and which has been compressedto a bulk of about 8-10 cm³/g has been kept for at least one week atambient temperature (e.g. 20° C.) and a specified relative humidity, forexample 50% RH.

While there are no specific restrictions as to the amount ofanti-bacterial agent to be used in the present invention, as long as theobject of the present invention is not compromised, the amount ofanti-bacterial agent is preferably at least 1×10⁻⁴ g, more preferably atleast 5×10⁻⁴ g, most preferably at least 1×10⁻³ g per g of dry absorbentcore. However, there are cases where the anti-bacterial agent can beused in amounts as low as 5 to 10 ppm of antibacterial agent(s) (byweight) in terms of the dry absorbent core. Such a case is Kathon® CG,which is a mixture of two compounds, namely5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one, Beyond a certain amount ofanti-bacterial agent (for instance 0.01 g or 0.1 g per g dry absorbentcore), it may no longer be economical to add further anti-bacterialagent.

The amount of alkali metal chloride or alkaline earth metal chloride,such as sodium chloride is at least 0.01 g, preferably at least 0.05 g,for instance at least 0.1 g per g dry absorbent core. There is nospecific upper limit for the (earth) alkali metal chloride content,although it may no longer be beneficial to increase the amount beyondvalues such as 0.5 g per g absorbent core or 1 g per g absorbent core.

Very low amounts of organic zinc salts cooperate already with component(i) in a very efficient odour control. A preferred lower weight limit oforganic zinc salt (calculated as zinc), such as zinc ricinoleate seemsto be at least 1×10⁻⁵ g per g of dry absorbent core. More preferredvalues are at least 1×10⁻⁴ g, even more preferably at least 5×10⁻⁴ g perg dry absorbent core, even more preferably at least 1×10⁻³ g per g ofdry absorbent core. There is no specific upper limit, even though foreconomic reasons, a point may be reached where it may no longer beuseful to further increase the zinc content, for instance to values of0.1 or 1 g zinc per g absorbent core, if this is not accompanied by anenhanced odour suppression.

The weight ratio of the anti-bacterial agent, alkali metal chloride oralkaline earth metal chloride, and the organic zinc salt is also notspecifically limited, but it is preferably 15/1 to 1/5, more preferably5/1 to 1/2, for instance 3/1 to 1/1.

The present invention is also not subject to any limitations regardingthe technique of incorporating the anti-bacterial agent or alkali metalor alkaline earth metal chloride (in the following also “the chloride”)and the organic zinc salt into the absorbent core. However, dipping,impregnation and spraying are preferred.

For instance, it is conceivable to treat the pulp fibers to be used inthe absorbent core, preferably cellulosic fluff pulp with a mixedsolution of the organic zinc salt prior to or during admixture with theSAP. In the alternative, the fibers to be used in the absorbent core canbe treated successively with separate solutions, e.g. by dipping andspraying, a first solution comprising the anti-bacterial agent or thechloride, and a second solution comprising the organic zinc salt.

According to one embodiment, the superabsorber (SAP) to be used in theabsorbent core is treated with a mixed solution of the organic zinc saltprior to or during admixture with the pulp fibers, in particularcellulosic fluff pulp. In the alternative, the SAP to be used in theabsorbent core can be treated successively with separate solutions, e.g.by dipping and spraying, a first solution comprising the anti-bacterialagent or the chloride, and a second solution comprising the organic zincsalt.

According to another embodiment, a mixed solution of the organic zincsalt and the anti-bacterial agent or chloride is sprayed onto thefibers, most preferably onto the cellulosic fluff pulp sheets asobtained from the manufacturer. The mixed solution can be sprayed ontothe fluff pulp sheet directly by the manufacturer of these sheets priorto the delivery of the sheets to the manufacturer of the absorbentarticles. This is an especially preferred embodiment since it avoids theextra step of spraying the mixed solution or the separate solutions(i.e. of the organic zinc salt and component (i)) when manufacturing theabsorbent article. Alternatively, the pulp sheet is dipped into thesolution. The SAP can be added during or after sheet formation to obtainan absorbent core treated in accordance with the present invention.

The most preferred way is to pretreat the SAP or the pulp fibers, inparticular the fluff pulp fibers, with a mixed solution or separatesolutions of the organic zinc salt and the anti-bacterial agent orchloride and to incorporate these components along with the pulp in theabsorbent core during core formation.

According to one preferred application technique, the solution(s) ofcomponent(i), in particular benzoic acid, and component(ii), inparticular zinc ricinoleate are sprayed on one or both sides of theabsorbent core, or one of both sides of the individual layersconstituting the same.

The solvent used for the mixed solution of (i) anti-bacterial agent orchloride and (ii) organic zinc salt can be water, a preferably volatileorganic solvent such as ethanol or a mixture of water and awater-miscible organic solvent such as ethanol, as long as thecomponents (i) and (ii) will dissolve or can be dispersed therein.Preferably, these solvents are also used when preparing two separatesolutions of component (i) and (ii). In the case of the two solutions,the solvents can be selected independently dependent on the solubilityof component (i) and the organic zinc salt. Preferably, the components(i) and (ii) are present in the solution(s) in a relatively highconcentration, preferably 1 to 30 wt.-%. The use of such concentratedsolutions ensures that the absorption capacity of the superabsorbentmaterial is not impaired more than necessary. Commercially availablesolutions of organic zinc salts such as TEGO® Sorb A30 available fromDegussa (content of actives 30 weight %, zinc ricinoleate activated byan amino acid), optionally in a diluted form, to which an appropriateamount of desired compound (i) is added, can also be employed.

The backsheet prevents the exudates absorbed by the absorbent layer andcontained within the article from soiling other external articles thatmay contact the absorbent article, such as bed sheets and undergarments.In preferred embodiments, the backsheet is substantially impervious toliquids (e.g., urine) and comprises a laminate of a nonwoven and a thinplastic film such as a thermoplastic film having a thickness of about0.012 mm to about 0.051 mm. Suitable backsheet films include thosemanufactured by Tredegar Industries Inc. of Terre Haute, Ind. and soldunder the trade names X15306, X10962, and X10964. Other suitablebacksheet materials may include breathable materials that permit vaporsto escape from the absorbent article while still preventing exudatesfrom passing through the backsheet. Exemplary breathable materials mayinclude materials such as woven webs, nonwoven webs, composite materialssuch as film-coated nonwoven webs, and microporous films.

The above elements of an absorbent article can be assembled, optionallytogether with other typical elements of absorbent articles in a mannerknown in the art.

The present invention is also concerned with cellulosic fibers, inparticular cellulosic fluff pulp fibers comprising components (i) and(ii) as specified above. The cellulosic fibers can be obtained bytreating the same in a manner as described above.

The following examples and comparative examples illustrate the presentinvention without limiting same.

EXAMPLE 1

Circular test absorbent cores having a weight of about 1.48 g and adiameter of 5 cm were punched out of an absorbent core produced in apilot plant. A standard method of mat forming a core was used in theproduction of the core in the pilot plant. The absorbent core consistedof a homogenous mixture of fluff pulp, sodium chloride andsuperabsorbent material. The fluff pulp used was 0.69 g Weyerhauser pulp(NB 416) and the superabsorbent material was 0.47 g of a superabsorber(Dow Chemicals XZ 91030.03). Sodium chloride (NaCl) was used in anamount of 163 g/m² (corresponding to 0.32 g/g dry absorbent core). Theabsorbent core was compressed to a bulk of about 8-10 cm³/g.

To the absorbent core, 1.3 ml of a solution containing 0.5 wt % zincricinoleate (available from Degussa under the tradename TEGO® Sorb A30and suitably diluted) was added by either dripping the solution onto thesurface (on one side) or dipping one side of the core into the solution.1 week after the treatment, the absorbent core was allowed to absorb 16ml synthetic urine according to Method A as described below and thenallowed to stand at room temperature.

6 h and 8 h after the absorption of synthetic urine the amount ofammonia developed was measured.

Five measurements were averaged as mean value. The results are shown inTable 1.

Method A: Measurement of Ammonia Inhibition in Absorbent Cores

Absorbent cores were prepared as described above. Test liquid 1 wasprepared. Bacteria suspension of Proteus mirabilis was cultivated innutrient broth 30° C. overnight. The graft cultures were diluted and thebacterial count was determined. The final culture containedapproximately 10⁵ bacteria per ml of test liquid. The absorbent core wasplaced in a plastic jar and the Test liquid 1 was added to the absorbentcore, whereafter the container was incubated at 35° C. 6 and 8 hours,respectively, whereafter samples were taken from the containers using ahand pump and a so called Dräger-tube. The ammonia content was obtainedas a colour change on a scale graded in ppm or volume percent.

Test Liquid 1:

Sterile synthetic urine to which has been added a growth medium formicro-organisms. The synthetic urine contains mono- and divalent cationsand anions and urea and has been prepared in accordance with theinformation in Geigy, Scientific Tables, Vol 2, 8^(th) ed. 1981 p. 53.The growth medium for the micro-organisms is based on information ofHook- and FSA-media for entero-bacteria. The pH in this mixture is 6.6.

COMPARATIVE EXAMPLE 1

An absorbent core was formed in the same manner as in Example 1, withthe exception that not treatment solution was applied to the absorbentcore so that it did not contain any zinc ricinoleate.

COMPARATIVE EXAMPLE 2

An absorbent core was formed in the same manner as in Example 1 with thesole difference that the core did not contain any sodium chloride(weight of absorbent core about 1.16 g) and that the solution used fortreating the absorbent core contained 6 wt % of zinc ricinoleate, and nosodium chloride.

The results in terms of ammonia formation of Example 1 and ComparativeExamples 1 and 2 are shown in the following Table 1.

TABLE 1 Ammonia Ammonia Formation Formation sample (ppm) (ppm)description 6 h 8 h CEx 1 NaCl 77 520 CEx 2 Zn¹ <19 270 Ex 1 NaCl + Zn¹10 140 ¹Zinc ricinoleate

The above experiments show that the combined use of an alkali metalchloride, such as sodium chloride, and an organic zinc salt, such aszinc ricinoleate suppresses the formation of ammonia to a verysurprising extent.

The invention claimed is:
 1. Absorbent article comprising a topsheet, abacksheet and an absorbent core enclosed between said topsheet and saidbacksheet, wherein said absorbent core comprises (i) an anti-bacterialagent or, in an amount of at least 0.01 g per g dry absorbent core, atleast one alkali metal or alkaline earth metal chloride, and (ii) anorganic zinc salt, wherein the amount of organic zinc salt is such thatat least 5 ×10⁻⁴ g Zn per g dry absorbent core is contained in theabsorbent core.
 2. Absorbent article comprising a topsheet, a backsheetand an absorbent core enclosed between said topsheet and said backsheet,wherein said absorbent core comprises (i) an anti-bacterial agent or, inan amount of at least 0.01 g per g dry absorbent core, at least onealkali metal or alkaline earth metal chloride, and (ii) an organic zincsalt, wherein the absorbent core comprises the anti-bacterial agent,wherein the amount of anti-bacterial agent is at least 1 ×10⁻³ g per gdry absorbent core.
 3. Absorbent article comprising a topsheet, abacksheet and an absorbent core enclosed between said topsheet and saidbacksheet, wherein said absorbent core comprises (i) an anti-bacterialagent or, in an amount of at least 0.01 g per g dry absorbent core, atleast one alkali metal or alkaline earth metal chloride, and (ii) anorganic zinc salt, wherein the absorbent core comprises theanti-bacterial agent, wherein the weight ratio of the anti\- bacterialagent and the organic zinc salt, in terms of zinc, is 15/1 to 1/5. 4.Absorbent article comprising a topsheet, a backsheet and an absorbentcore enclosed between said topsheet and said backsheet, wherein saidabsorbent core comprises (i) an anti-bacterial agent or, in an amount ofat least 0.01 g per g dry absorbent core, at least one alkali metal oralkaline earth metal chloride, and (ii) an organic zinc salt, whereinthe absorbent core comprises the anti-bacterial agent, wherein theanti-bacterial agent is selected from the group consisting of organicacids and polyacids, and their salts, having 2 to 18 carbon atoms. 5.Absorbent article according to claim 4, wherein the organic acid orpolyacid is selected from the group consisting of saturated orunsaturated linear or branched carboxylic acids having from 3 to 8carbon atoms and aromatic acids and polyacids having from 7 to 10 carbonatoms.
 6. Absorbent article according to claim 5, wherein the acid orpolyacid is selected from the group consisting of benzoic acid, sorbicacid, tartaric acid, citric acid, and mixtures thereof.
 7. Absorbentarticle according to claim 6, wherein the acid is benzoic acid. 8.Absorbent article comprising a topsheet, a backsheet and an absorbentcore enclosed between said topsheet and said backsheet, wherein saidabsorbent core comprises (i) an anti-bacterial agent or, in an amount ofat least 0.01 g per g dry absorbent core, at least one alkali metal oralkaline earth metal chloride, and (ii) an organic zinc salt, whereinthe organic zinc salt is selected from zinc salts of carboxylic acidshaving 2 to 30 carbon atoms.
 9. Absorbent article according to claim 8,wherein the carboxylic acid represents an unsaturated hydroxylated fattyacid having 8 to 18 carbon atoms.
 10. Absorbent article according toclaim 9, wherein the zinc salt is zinc ricinoleate.
 11. Absorbentarticle comprising a topsheet, a backsheet and an absorbent coreenclosed between said topsheet and said backsheet, wherein saidabsorbent core comprises (i) an anti-bacterial agent or, in an amount ofat least 0.01 g per g dry absorbent core, at least one alkali metal oralkaline earth metal chloride, and (ii) an organic zinc salt, whereinthe absorbent core comprises the anti-bacterial agent, wherein theanti-bacterial agent is benzoic acid and the zinc salt is zincricinoleate.